The Sun Is a Beautifully Blank Billiard Ball for Halloween

For the festive season, our nearest star is keeping its choice of costume simple.

I’m not saying the Sun isn’t being creative, it’s just not putting too much effort into this year’s stellar fancy dress party. I mean, look at it:

The Sun right now, as seen by the Helioseismic and Magnetic Imager (HMI) instrument on NASA’s Solar Dynamics Observatory (SDO) [NASA/SDO]

That flawless orange billiard ball is the photosphere of our Sun. Have you ever seen something so smooth and beautifully unremarkable?

Well, you have now, and its blank gaze is actually the reason why it’s causing a bit of a stir. According to our ever watchful solar sentry, Tony Phillips at, the northern summer of 2019 may go down in history as “the summer without sunspots.”

From June 21st until Sept 22nd, the sun was blank more than 89% of the time. During the entire season only 6 tiny sunspots briefly appeared, often fading so quickly that readers would complain to, “you’ve labeled a sunspot that doesn’t exist!” (No, it just disappeared.) Not a single significant solar flare was detected during this period of extreme quiet.

Dr. Tony Phillips

So, what does this mean?

Sunspots are the visual cues for magnetic turmoil within our nearest star. Over cycles of approximately 11 years, the Sun’s internal magnetic field becomes stretched and twisted, driving the ebb and flow of space weather.

Starting with our solar billiard ball here, suffice to say that the solar magnetic field is pretty untwisted and, well, chilled. This is the epitome of “solar minimum” — and, as commented on by Phillips, a deep, potentially record-breaking solar minimum at that. It’s very likely that this is as minimum as solar minimum can be, so we could hazard a guess to say that things are going to start getting interesting very soon.

Differential rotation and the formation of coronal loops as demonstrated by my awesome abilities as a Microsoft Word artist [source: my PhD thesis!]

As our Sun is a massive blob of magnetized plasma, it doesn’t rotate uniformly (like the Earth does), it actually rotates a little faster at its equator than at its poles, a phenomenon known as “differential rotation.” Now, if you imagine the solar magnetic field as straight lines running from pole to pole, you can imagine that, over time, the field will start to wrap around the equator like an elastic band being stretched out of shape and wrapped around the middle. At its most extreme, so much rotational tension will be applied to the magnetic field that it becomes contorted. This contortion creates an upward pressure, forcing vast loops of magnetized plasma, known as coronal loops, to pop through the Sun’s photosphere — a.k.a. the solar “surface” — like annoyingly twisted loops of garden hosepipe (see the diagram above).

As its most extreme, in a few years time, we can expect our boring ol’ billiard ball to look something like this:

The Sun in 2014 (during the previous solar maximum), as seen by the SDO’s HMI [NASA/SDO]

About those blotches: those dark spots are sunspots and they are a direct consequence of the magnetic turmoil that rumbles inside the Sun during solar maximum. Remember those coronal loops I was talking about? Well, these huge, beautiful arcs of plasma cause the hotter outer layers of the Sun to be pushed aside, exposing the comparatively cooler (though still thousands of degrees) plasma under the surface — that’s what creates those dark blotches. And by counting sunspots, you can gauge how magnetically active the Sun is.

By viewing the Sun in different wavelengths, we can view the Sun’s atmosphere at different temperatures and, as the Sun’s atmosphere (the corona) is counter-intuitively hotter the higher above the surface you get, let’s take a look at what solar maximum looks like above these sunspots:

Yikes! The Sun’s corona in October 2014 (during the previous solar maximum), as seen by the SDO’s Atmospheric Imaging Assembly (AIA) instrument. And a damn fine effort just in time for Halloween. [NASA/SDO]

As you can see, there’s a lot of coronal loops erupting through the surface, creating huge regions of activity (called active regions, unsurprisingly). And the above observation was captured on Oct. 8, 2014, when the Sun was, apparently, in a terrifyingly festive Halloween mood! These regions can be hothouses for solar flares and coronal mass ejections; explosive phenomena that can have dramatic space weather effects on Earth.

So that was solar maximum; what does the solar corona look like now, at solar minimum?

The Sun’s corona right now, as seen by the SDO’s AIA [NASA/SDO]

Yep, as you guessed, very relaxed. In this state, we can expect very little in the way of explosive space weather events, such as flares and CMEs; there’s simply too little magnetic energy at solar minimum to create many surprises (caveat: even solar minimum can generate flares, they’re just few and far between).

While the Sun may look boring, the effects of space weather are anything but. During these times of solar minimum, the extended solar magnetic field (called the heliosphere), a magnetic bubble that reaches beyond the orbits of all the planets, contracts and weakens, allowing more cosmic rays from energetic events from the rest of the cosmos to reach Earth. Cosmic rays are ionizing particles that can boost the radiation exposure of astronauts and frequent fliers. Also, the solar wind can become a more persistent presence; streams of energized particles that are continuously streaming from the lower corona, so we still get our aurorae at high latitudes.

Recognition that the Sun is now in a deep minimum means the solar vacation is nearing an end. Astronomers have reported that of the handful of sunspots have made an appearance over the last few months with a flip in magnetic polarity, which can mean only one thing: Solar Cycle 25 is coming and the next solar maximum is only four years away.

When the Sun is So Boring, Anything Becomes Interesting

Caption: So boring it doesn't deserve a caption (NASA/SOHO)
Caption: So boring it doesn't deserve a caption (NASA/SOHO)

You know when you have those unremarkable days, those periods of time you experience you know you’ll forget tomorrow? It’s either “just another” day at work, another commute, or a Sunday where you had a beer, fell asleep, only to wake up again to realise it was too late to get up so you stayed in bed till Monday? (And no, I don’t make a habit of that. I’m sure to have at least two beers.) Most days aren’t like that for me, usually I can think of one noteworthy event that sets apart one day from the next, but sometimes it’s as if Stuff Happens™ doesn’t.

It would appear the Sun is having an extended period of time where Stuff Happens™ is at a premium, so you have to make the most of when something really does happen. In this case, the Sun released a crafty CME, thinking we wouldn’t see it…
Continue reading “When the Sun is So Boring, Anything Becomes Interesting”

Our (Painfully) Featureless Sun

The Sun, being boring on Jan. 13th 2009, a whole year after Solar Cycle 24 was supposed to start (solar astrophotography by ©Stephen Sykes)
The Sun, being boring on Jan. 13th 2009, a whole year after Solar Cycle 24 was supposed to start (solar astrophotography by ©Stephen Sykes)

This morning I realised it’s been a whole year since we saw the first reversed polarity sunspot pair on the surface of the Sun. A year ago, Solar Cycle 23 was running out of steam and Cycle 24 was about to take over. Solar physicists the world over were making predictions, some thought Cycle 24 was going to be a “doozy”, others were a little more conservative, saying it might just be an “average” cycle. However, 12 months on, it would appear Cycle 24 is off to a very lazy start. Once again, we have a “blank” Sun, a perfect sphere, looking like a marble, or as my wife observed: a jawbreaker (or as us Brits like to expressively call them, gobstoppers).

The stunning image above was shot by skilled astrophotographer Stephen Sykes, over at, demonstrating what superb views of the Sun can be captured by amateur astronomers. When I (eventually) get my telescope, and/or a new camera, the Sun will be my first astronomical object to observe, but I doubt I’ll get as good a view as this.

So, another day, another featureless Sun. That’s not to say it’s been a totally boring year; we’ve had flares from “left over” active regions from Cycle 23 and we’ve had a bit of action from Cycle 24 (the most recent set of spots–Sunspot 1010–have just rotated out of view), and I’m pretty sure this time next year we’ll be inundated with sunspots… fingers crossed (I can’t wait to see some coronal loop arcades again). For now, good night our lazy Sun, I look forward to seeing more action in the coming months…

Cycle 24 Sunspot Observed… At Last!

Thar she blows! Solar Cycle 24 sunspots make their first appearence since January (SOHO MDI image showing Cycle 24 polarity)
Thar she blows! Solar Cycle 24 sunspots make their first appearence since January (SOHO MDI image showing Cycle 24 polarity)

This day has been a long time coming. Ever since the beginning of Solar Cycle 24 back on January 4th 2008, solar physicists have been eagerly awaiting the fireworks to begin… alas, the Sun decided to take a break and stay blank for nine months, keeping any Cycle 24 sunspot activity hidden. That’s not to say there have been no sunspots. Due to a strange quirk in solar activity, the previous cycle took some time to wind down and continued to send groups of spots to the surface, occasionally unleashing some surprise flares and coronal mass ejections (CMEs).

However, it has now been confirmed that the sunspot group seen today by the Solar and Heliospheric Observatory (SOHO) and international amateur astronomers do in fact belong to Cycle 24.

Phew, I was beginning to feel a little chilly
Continue reading “Cycle 24 Sunspot Observed… At Last!”

Breaking News: We Have Sunspots, First for Over a Month

New sunspots observed on Aug. 21st (© Pavol Rapavy)
New sunspots observed on Aug. 21st (© Pavol Rapavy)

Just as we were getting concerned that the Sun may be facing an extended solar minimum, amateur astronomers, in the last few hours, have observed a new sunspot pair appearing around the Sun’s south-eastern limb. They are young, emergent spots, gradually getting larger. It will be interesting to see how they evolve. The observation above was taken by Pavol Rapavy in Rimavska Sobota, Slovakia, and now we have detailed images of the region by a British astronomer too (sounds like the Sun might be making an appearance for the UK summer at last!)…
Continue reading “Breaking News: We Have Sunspots, First for Over a Month”